U.S. patent number 10,271,337 [Application Number 15/505,243] was granted by the patent office on 2019-04-23 for method and apparatus for performing decoding with low complexity in wireless communication system.
This patent grant is currently assigned to Samsung Electronics Co., Ltd.. The grantee listed for this patent is Samsung Electronics Co., Ltd. Invention is credited to Seok-Ki Ahn, Sung-Nam Hong, Chi-Woo Lim, Woo-Myoung Park, Min Sagong.
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United States Patent |
10,271,337 |
Sagong , et al. |
April 23, 2019 |
Method and apparatus for performing decoding with low complexity in
wireless communication system
Abstract
The present disclosure relates to a pre-5.sup.th-Generation (5G)
or 5G communication system to be provided for supporting higher
data rates Beyond 4.sup.th-Generation (4G) communication system
such as Long Term Evolution (LTE). The present invention relates to
method and apparatus for performing a decoding with low complexity
in a wireless communication system. A decoding method of a terminal
in a wireless communication system comprises determining a first
characteristic value indicating a statistical characteristic of an
interference signal based on a received signal of a base station,
determining a second characteristic value indicating a statistical
characteristic of an interference signal based on data received
from the base station, and decoding the data according to a
decoding scheme corresponding to a difference of the first
characteristic value and the second characteristic value.
Inventors: |
Sagong; Min (Gyeonggi-do,
KR), Park; Woo-Myoung (Gyeonggi-do, KR),
Ahn; Seok-Ki (Gyeonggi-do, KR), Lim; Chi-Woo
(Gyeonggi-do, KR), Hong; Sung-Nam (Gyeonggi-do,
KR) |
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Electronics Co., Ltd |
Gyeonggi-do |
N/A |
KR |
|
|
Assignee: |
Samsung Electronics Co., Ltd.
(Suwon-si, KR)
|
Family
ID: |
55350967 |
Appl.
No.: |
15/505,243 |
Filed: |
August 20, 2015 |
PCT
Filed: |
August 20, 2015 |
PCT No.: |
PCT/KR2015/008680 |
371(c)(1),(2),(4) Date: |
February 20, 2017 |
PCT
Pub. No.: |
WO2016/028094 |
PCT
Pub. Date: |
February 25, 2016 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20170265200 A1 |
Sep 14, 2017 |
|
Foreign Application Priority Data
|
|
|
|
|
Aug 20, 2014 [KR] |
|
|
10-2014-0108416 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L
1/1887 (20130101); H04B 17/345 (20150115); H04L
5/0057 (20130101); H04L 27/0008 (20130101); H04W
72/082 (20130101); H04L 27/10 (20130101); H04L
1/00 (20130101); H04B 17/26 (20150115); H04L
27/364 (20130101); H04W 72/0413 (20130101); H04L
5/0035 (20130101); H04L 5/0023 (20130101) |
Current International
Class: |
H04W
72/08 (20090101); H04L 27/36 (20060101); H04L
27/10 (20060101); H04W 72/04 (20090101); H04B
17/26 (20150101); H04L 5/00 (20060101); H04L
1/18 (20060101); H04L 1/00 (20060101); H04B
17/345 (20150101); H04L 27/00 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
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|
|
|
|
1020140081751 |
|
Jul 2014 |
|
KR |
|
1020140081753 |
|
Jul 2014 |
|
KR |
|
2014098536 |
|
Jun 2014 |
|
WO |
|
Other References
International Search Report dated Dec. 8, 2015 in connection with
International Application No. PCT/KR2015/008680, 5 pages. cited by
applicant .
Written Opinion of the International Searching Authority dated Dec.
8, 2015 in connection with International Application No.
PCT/KR2015/008680, 4 pages. cited by applicant .
Sungnam Hong, et al., "A Modulation Technique for Active
Interference Design Under Downlink Cellular OFDMA Networks", IEEE,
2014, 6 pages. cited by applicant .
Changkyu Seol, et al., "A Statistical Inter-Cell Interference Model
for Downlink Cellular OFDMA Networks Under Log-Normal Shadowing and
Multipath Rayleigh Fading", IEEE Transactions on Communications,
vol. 1, No. X, XXX, 2009, 10 pages. cited by applicant.
|
Primary Examiner: Yao; Kwang B
Assistant Examiner: Jeong; Moo
Claims
The invention claimed is:
1. A method for operating a terminal in a wireless communication
system, comprising: determining a first characteristic value
indicating a non-Gaussian level of an interference signal based on
a received signal from a base station; determining a second
characteristic value indicating a non-Gaussian level of an
interference signal based on data received from the base station;
and decoding the data according to a decoding scheme corresponding
to a difference between the first characteristic value and the
second characteristic value.
2. The method of claim 1, wherein decoding the data according to
the decoding scheme corresponding to the difference between the
first characteristic value and the second characteristic value
comprises: determining a mismatch metric corresponding to the
difference between the first characteristic value and the second
characteristic value based on at least one of a size of the first
characteristic value, a size of the second characteristic value, an
increase range of a characteristic value, a quantization level, or
a scale parameter; and determining the decoding scheme for the data
based on the mismatch metric.
3. The method of claim 2, wherein determining the decoding scheme
for the data based on the mismatch metric comprises: determining
the decoding scheme for the data based on a comparison of the
mismatch metric with at least one threshold.
4. The method of claim 1, wherein the decoding scheme comprises at
least one of a scheme for omitting a decoding procedure for the
data and determining a decoding failure for the data, a scheme for
adjusting at least one pre-determined decoding parameter, or a
scheme for using a pre-determined decoding parameter.
5. The method of claim 1, further comprising: transmitting, to the
base station, a decoding result of the data and information
regarding the difference between the first characteristic value and
the second characteristic value.
6. The method of claim 1, further comprising: transmitting, to the
base station, a message for requesting scheduling for resource
allocation based on the difference between the first characteristic
value and the second characteristic value.
7. An apparatus of a terminal in a wireless communication system,
the apparatus comprising: at least one transceiver; and at least
one processor, operatively coupled to the at least one transceiver,
configured to: determine a first characteristic value indicating a
non-Gaussian level of an interference signal based on a received
signal from a base station; determine a second characteristic value
indicating a non-Gaussian level of an interference signal based on
data received from the base station; and decode the data according
to a decoding scheme corresponding to a difference between the
first characteristic value and the second characteristic value.
8. The apparatus of claim 7, wherein the at least one processor is
further configured to: determine a mismatch metric corresponding to
the difference between the first characteristic value and the
second characteristic value based on at least one of a size of the
first characteristic value, a size of the second characteristic
value, an increase range of a characteristic value, a quantization
level, or a scale parameter; and determine the decoding scheme for
the data based on the mismatch metric.
9. The apparatus of claim 8, wherein the at least one processor is
further configured to: determine the decoding scheme for the data
based on comparison of the mismatch metric with at least one
threshold.
10. The apparatus of claim 9, wherein the at least one threshold
indicates a level of non-Gaussianity of a channel between the
terminal and the base station.
11. The apparatus of claim 7, wherein the decoding scheme comprises
at least one of a scheme for omitting a decoding procedure for the
data and determining a decoding failure for the data, a scheme for
adjusting at least one pre-determined decoding parameter, or a
scheme for using a pre-determined decoding parameter.
12. The apparatus of claim 7, wherein the at least one transceiver
is further configured to: transmit, to the base station, a decoding
result of the data and information regarding the difference between
the first characteristic value and the second characteristic
value.
13. The apparatus of claim 7, wherein the at least one transceiver
is further configured to: transmit, to the base station, a message
for requesting scheduling for resource allocation based on the
difference between the first characteristic value and the second
characteristic value.
14. An apparatus of a base station in a wireless communication
system, the apparatus comprising: at least one transceiver
configured to receive, from a terminal, information regarding a
data decoding result and a difference between a first
characteristic value and a second characteristic value; and at
least one processor configured to perform scheduling for the
terminal based on the decoding result and the information regarding
the difference between the first characteristic value and the
second characteristic value, wherein the first characteristic value
indicates a non-Gaussian level of an interference determined based
on a signal transmitted to the terminal, and the second
characteristic value indicates a non-Gaussian level of an
interference determined based on the data.
15. The apparatus of claim 14, wherein the at least one processor
is further configured to: compare the difference between the first
characteristic value and the second characteristic value with at
least one threshold; and perform at least one of a function related
to hybrid automatic repeat request (HARQ) or a change of allocated
resources for the terminal according to a result of the
comparison.
16. The apparatus of claim 15, wherein the at least one processor
is further configured to: perform at least one scheme of chase
combining, retransmission, or incremental redundancy (IR).
17. The apparatus of claim 15, wherein the at least one processor
is further configured to: when the difference between the first
characteristic value and the second characteristic value is smaller
than a preset threshold, allocate a fixed resource region from
among a whole resource region of the base station, to the
terminal.
18. The apparatus of claim 15, wherein the at least one processor
is further configured to: adjust a size of a fixedly allocated
resource region for a specific modulation scheme based on a number
of terminals of which the difference between the first
characteristic value and the second characteristic value is smaller
than a preset threshold.
19. The apparatus of claim 14, wherein the at least one transceiver
is further configured to receive a message for requesting
scheduling for resource allocation from the terminal based on the
difference between the first characteristic value and the second
characteristic value, and wherein the at least one processor is
further configured to adjust a size of a fixedly allocated resource
region for a specific modulation scheme based on a number of
terminals that transmit a message requesting scheduling for the
resource allocation.
20. The apparatus of claim 14, wherein the at least one transceiver
is further configured to: transmit information regarding the
difference between the first characteristic value and the second
characteristic value to at least one neighboring base station,
receive information about a difference between a third
characteristic value and a fourth characteristic value of a
terminal connected to the neighboring base station, from the
neighboring base station, and wherein the at least one processor is
further configured to change a resource allocation region of the
terminal connected to the neighboring base station based on the
information about the difference between the third characteristic
value and the fourth characteristic value received from the
neighboring base station.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
The present application claims priority under 35 U.S.C. .sctn. 365
to International Patent Application No. PCT/KR2015/008680 filed
Aug. 20, 2015, entitled "METHOD AND APPARATUS FOR PERFORMING
DECODING WITH LOW COMPLEXITY IN WIRELESS COMMUNICATION SYSTEM",
and, through International Patent Application No.
PCT/KR2015/008680, to Korean Patent Application No. 10-2014-0108416
filed Aug. 20, 2014, each of which are incorporated herein by
reference into the present disclosure as if fully set forth
herein.
TECHNICAL FIELD
The present invention relates to a method and an apparatus for
determining a decoding operation in a wireless communication
system.
BACKGROUND ART
To meet the demand for wireless data traffic having increased since
deployment of 4th generation (4G) communication systems, efforts
have been made to develop an improved 5th generation (5G) or pre-5G
communication system. Therefore, the 5G or pre-5G communication
system is also called a `Beyond 4G Network` or a `Post LTE
System`.
The 5G communication system is considered to be implemented in
higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to
accomplish higher data rates. To decrease propagation loss of the
radio waves and increase the transmission distance, the
beamforming, massive multiple-input multiple-output (MIMO), Full
Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming,
large scale antenna techniques are discussed in 5G communication
systems.
In addition, in 5G communication systems, development for system
network improvement is under way based on advanced small cells,
cloud Radio Access Networks (RANs), ultra-dense networks,
device-to-device (D2D) communication, wireless backhaul, moving
network, cooperative communication, Coordinated Multi-Points
(CoMP), reception-end interference cancellation and the like.
In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and sliding
window superposition coding (SWSC) as an advanced coding modulation
(ACM), and filter bank multi carrier (FBMC), non-orthogonal
multiple access (NOMA), and sparse code multiple access (SCMA) as
an advanced access technology have been developed.
In general, a wireless communication system assumes a Gaussian
distribution with respect to an interference signal to conduct
decoding with low complexity. That is, to make characteristics of
the interference signal as close to the Gaussian distribution as
possible, the QAM modulation scheme is mostly used. However, since
it is known that a channel capacity of a non-Gaussian channel is
greater than a Gaussian channel, when the decoding is conducted
properly, a higher decoding performance can be obtained in the
non-Gaussian channel than the Gaussian channel. Thus, it was
required to develop a modulation scheme allowing the
characteristics of the interference signal to exhibit the
non-Gaussian distribution, and as a result, a suggested modulation
scheme is the FQAM. The FQAM is a hybrid modulation scheme
combining the QAM and the FSK, and can include all of advantages of
high spectrum efficiency of the QAM and a non-Gaussian interference
signal of the FSK.
When the FQAM is used in an interference cell, statistical
characteristic of the interference signal becomes non-Gaussian and
accordingly a non-Gaussian decoding method needs to be used to
enhance the performance through the FQAM. The non-Gaussian decoding
method is a decoding method using a statistical characteristic
value (hereafter, referred to as an `alpha value) of the
interference signal. To systematically operate the non-Gaussian
decoding method, it is required to calculate the alpha value in the
process of Channel Quality Indicator (CQI) calculation and to
calculate the alpha value in the process of data decoding as well.
To minimize a performance loss, there should be no difference
between the alpha value of the CQI calculation and the alpha value
of the data decoding. However, in the system operation, a
difference value inevitably occurred between the alpha value of the
CQI calculation and the alpha value of the data decoding.
DISCLOSURE OF INVENTION
Technical Problem
Accordingly, an embodiment of the present invention to provide a
method and an apparatus for determining a decoding operation of a
terminal based on an alpha value in the terminal.
Another embodiment of the present invention to provide a method and
an apparatus for calculating a mismatch metric of an alpha value
for Channel Quality Indicator (CQI) calculation and an alpha value
for data decoding in a terminal.
Yet another embodiment of the present invention to provide a method
and an apparatus for controlling a decoding operation based on a
mismatch metric of an alpha value for CQI calculation and an alpha
value for data decoding in a terminal.
Still embodiment of the present invention to provide a method and
an apparatus for controlling Hybrid Automatic Repeat reQuest (HARQ)
based on a mismatch metric received from a terminal in a base
station.
A further embodiment of the present invention to provide a method
and an apparatus for performing resource allocation control
scheduling of a terminal based on a mismatch metric received from a
terminal in a base station.
Solution to Problem
According to an embodiment of the present invention, a method for
operating a terminal in a wireless communication system comprises
determining a first characteristic value indicating a statistical
characteristic of an interference signal based on a received signal
of a base station, determining a second characteristic value
indicating a statistical characteristic of an interference signal
based on data received from the base station, and decoding the data
according to a decoding scheme corresponding to a difference of the
first characteristic value and the second characteristic value.
According to an embodiment of the present invention, a method for
operating a base station in a wireless communication system
comprises receiving information regarding a data decoding result
and a difference of a first characteristic value and a second
characteristic value from a terminal, and performing scheduling for
the terminal based on the decoding result and the information about
the difference of the first characteristic value and the second
characteristic value. The first characteristic value indicates a
statistical characteristic for an interference determined based on
a signal transmitted to the terminal, and the second statistical
characteristic value indicates a statistical characteristic for an
interference determined based on the data.
According to an embodiment of the present disclosure, an apparatus
of a terminal in a wireless communication system comprises at least
one transceiver and at least one processor, operatively coupled to
the at least one transceiver. The at least one processor is further
configured to determine a first characteristic value indicating a
statistical characteristic of an interference signal based on a
received signal from a base station, determine a second
characteristic value indicating a statistical characteristic of an
interference signal based on data received from the base station,
and decode the data according to a decoding scheme corresponding to
a difference of the first characteristic value and the second
characteristic value.
According to an embodiment of the present disclosure, an apparatus
of a base station in a wireless communication system comprises at
least one transceiver configured to receive, from a terminal,
information regarding a data decoding result and a difference of a
first characteristic value and a second characteristic value, and
at least one processor configured to perform scheduling for the
terminal based on the decoding result and the information regarding
the difference of the first characteristic value and the second
characteristic value. The first characteristic value indicates a
statistical characteristic for an interference determined based on
a signal transmitted to the terminal, and the second statistical
characteristic value indicates a statistical characteristic for an
interference determined based on the data.
Advantageous Effects of Invention
A terminal according to an embodiment of the present invention can
calculate a mismatch metric of an alpha value for Channel Quality
Indicator (CQI) calculation and an alpha value for data decoding,
control a decoding operation based on the calculated mismatch
metric, and thus enhance a decoding performance of the terminal and
perform reliable communication.
A base station according to an embodiment of the present invention
can control Hybrid Automatic Repeat reQuest (HARQ) based on the
mismatch metric received from the terminal, perform scheduling of
the terminal, and thus enhance the decoding performance of the
terminal and execute the reliable communication.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a flowchart illustrating a decoding operation of a
terminal and a scheduling procedure of a base station based on a
mismatch metric of alpha values in a wireless communication system
according to an embodiment of the present invention.
FIG. 2 is a block diagram of a terminal according to an embodiment
of the present invention.
FIG. 3 is a block diagram of a base station according to an
embodiment of the present invention.
FIG. 4 is a flowchart illustrating a procedure for decoding data
based on a mismatch metric of alpha values in a terminal according
to an embodiment of the present invention.
FIG. 5 is a flowchart illustrating a procedure for scheduling based
on a mismatch metric of alpha values in a base station according to
an embodiment of the present invention.
FIG. 6 is a graph showing a decoding performance difference
determined by an alpha value in a terminal according to an
embodiment of the present invention.
FIG. 7 is a graph for determining a decoding method of a terminal
according to an alpha value in a terminal according to an
embodiment of the present invention.
FIG. 8 is a graph for determining a decoding method of a terminal
according to an alpha value in the terminal according to another
embodiment of the present invention.
FIG. 9 is a graph for determining a decoding method of a terminal
according to an alpha value in the terminal according to yet
another embodiment of the present invention.
FIG. 10 is a graph for performing Hybrid Automatic Repeat reQuest
(HARQ) based on a decoding result in a base station according to an
embodiment of the present invention.
FIGS. 11A and 11B are diagrams depicting a resource allocation
status based on a mismatch metric of a terminal in a base station
according to an embodiment of the present invention.
FIG. 12 is a diagram depicting a resource allocation status of a
terminal in a base station according to an embodiment of the
present invention.
FIGS. 13A and 13B are diagrams depicting resource allocation status
change of neighboring base stations according to change of a
mismatch metric value of a first terminal according to an
embodiment of the present invention.
FIG. 14 is a curve graph showing a Signal to Noise Ratio (SNR), a
modulation scheme, and a coding rate corresponding to a first alpha
value according to an embodiment of the present invention.
FIG. 15 is a diagram showing a table indicating a mismatch metric
of an alpha value for Channel Quality Indicator (CQI) and an alpha
value for data decoding according to an embodiment of the present
invention.
FIG. 16 is a curve graph showing a performance gain based on the
number of decoding iterations in a terminal according to an
embodiment of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of the present invention is
described in detail with reference to the accompanying drawings. In
the following explanations of the present invention, specific
descriptions on well-known functions or constitutions will not be
described in detail if they would unnecessarily obscure the subject
matter of the present invention. Also, terminologies to be
described below are defined in consideration of functions in the
present invention and can vary depending on a user's or an
operator's intention or practice. Thus, their definitions should be
defined based on all the contents of the specification.
Hereafter, an embodiment of the present invention can enhance a
decoding performance by a terminal's determining a first alpha
value for Channel Quality Indicator (CQI) calculation based on a
pilot signal received from a base station, determining a second
alpha value for data decoding based on data received from the base
station, determining a mismatch metric according to a difference
value of the determined first alpha value and second alpha value,
and determining a decoding operation of the terminal based on the
determined mismatch metric. Also, since the base station receives a
decoding result of the terminal and the determined metric from the
terminal and conducts scheduling for the terminal, an embodiment of
the present invention can enhance a decoding performance of the
terminal and carry out reliable communication.
FIG. 1 is a flowchart illustrating a decoding operation of a
terminal and a scheduling procedure of a base station based on a
mismatch metric of alpha values in a wireless communication system
according to an embodiment of the present invention.
Referring to FIG. 1, a wireless communication network according to
an embodiment of the present invention can include a terminal 101
and a base station 103.
The base station 103 can send a pilot signal to the terminal 101 in
step 111. For example, the base station 103 can send the pilot
signal for channel estimation of the terminal. At this time, the
signal for the channel estimation of the terminal is not limited to
the pilot signal and can be other signal enabling the channel
estimation of the terminal. For example, the other signal enabling
the channel estimation of the terminal can be a reference signal, a
sync signal, a preamble signal, and the like.
The terminal 101 receives the pilot signal from the base station
103, and calculates a first alpha value for CQI calculation based
on a pilot signal reception result in step 113. At this time, the
alpha value (e.g., the first alpha value) indicates a statistic
characteristic value of Inter Cell Interference (ICI). For example,
the alpha value is a parameter representing a non-Gaussian
characteristic, and can be calculated based on a Complex
Generalized Gaussian (CGG) model of Equation 1 using Equation 2.
Here, the non-Gaussian characteristic can indicate whether
interference or noise of a channel follows a non-Gaussian
distribution, or indicate a non-Gaussian level of the interference
or the noise of the channel.
.function..alpha..times..pi..times..times..beta..times..GAMMA..function..-
alpha..times..function..beta..alpha..times..times. ##EQU00001##
Here, f.sub.CG indicates a probability density function (pdf) of
the channel interference or noise, x denotes a variable indicating
the channel interference or noise, and .alpha. denotes a shape
parameter indicating how much the CGG distribution is away from a
complex Gaussian distribution. Also, .GAMMA.(x) is a Gamma
function, and .GAMMA.(x).intg..sub.0.sup..infin.t.sup.z-1 exp(-t)dt
is defined. Also, .beta. denotes a scale parameter.
.alpha..function..function..times..function..times..function..pi..functio-
n..times..times..times. ##EQU00002##
Here, {circumflex over (.alpha.)} denotes the first alpha value,
N.sub.s denotes the number of Quadrature Amplitude Modulation (QAM)
symbols in a code frame, and Z[k] denotes a signal after a
channel-compensated signal is removed from a received signal.
Accordingly, Z[k] for the first alpha value calculation indicates a
signal produced by removing a channel-compensated pilot signal from
a received pilot signal.
Next, the terminal 101 can calculate the CQI based on the
calculated first alpha value in step 115. According to an
embodiment, the terminal 101 can determine the CQI based on a
pre-stored table or curve graph indicating the CQI based on a
Signal to Noise Ratio (SNR) and an alpha value. For example, the
terminal 101 can determine as the CQI, a modulation scheme and a
coding rate corresponding to the SNR and the first alpha value for
a pilot signal using a pre-obtained curve graph as shown in FIG.
14. For example, when the SNR is 8.8 dB and the first alpha value
is 0.5, the terminal 101 can determine a modulation level as 16FQAM
including 4FSK and 4QAM and determine the coding rate as 1/3. Here,
the curve graph showing the CQI based on the SNR and the alpha
value can be obtained or stored in advance through experiments.
According to another embodiment, the terminal 101 may calculate the
CQI based on the first alpha value using a conventional known
method. According to yet another embodiment, the terminal 101 can
determine a Modulation and Coding Scheme (MCS) based on a spectrum
efficiency corresponding to the SNR and the first alpha value.
Herein, the spectrum efficiency can indicate the number of bits
transmittable within a unit resource. Additionally, when
calculating the CQI, the terminal 101 can determine a decoding
parameter.
Next, the terminal 101 reports the calculated CQI and/or the first
alpha value to the base station 103 in step 117. For example, the
terminal 101 may report both of the CQI and the first alpha value
or either the CQI or the first alpha value to the base station 103
in step 117. The CQI can include at least one of the modulation
level, the coding rate, and the SNR. After receiving the CQI and/or
the first alpha value from the terminal 101, the base station 103
can transmit the MCS and data to the terminal 101 in step 119.
Here, the base station 103 can determine the MCS based on the CQI
and/or the first alpha value received from the terminal 101. For
example, when receiving the SNR and the first alpha value from the
terminal 101, the base station 103 can determine the modulation
level coding rate corresponding to the received SNR and first alpha
value by referring to the curve graph as shown in FIG. 14.
After receiving the MCS and the data from the base station 103, the
terminal 101 can calculate a second alpha value for decoding the
received data in step 121. For example, the terminal 101 can
calculate the second alpha value indicating a non-Gaussian level of
interference or noise of a current channel based on a data
reception result. Here, the second alpha value can be calculated in
the same manner as the first alpha value calculation based on
Equations 1 and 2. The calculation method of the second alpha value
is different from the first alpha value calculation method in that
Z[k] of Equation 2 denotes a resulting signal by removing the
channel compensated data signal from the received data signal.
Here, the channel compensated data signal can indicate a hard
decision result of the received signal.
Next, the terminal 101 can determine a mismatch metric based on a
difference of the first alpha value calculated for the CQI
calculation and the second alpha value calculated for the data
decoding in step 123. According to an embodiment of the present
invention, the mismatch metric of the first alpha value and the
second alpha value can be calculated using Equation 3.
.times..times..alpha..times..times..times..times..times..alpha..times..ti-
mes..times..DELTA..function..alpha..alpha..times..times.
##EQU00003##
Here, M denotes the mismatch metric of the first alpha value and
the second alpha value, .alpha..sub.CQI denotes the first alpha
value calculated for the CQI calculation, and .alpha..sub.DATA
denotes the second alpha value calculated for the data decoding.
Also, sgn denotes a sign function. Also, .alpha..sub.max indicates
the greater value of .alpha..sub.CQI and .alpha..sub.DATA, and
.alpha..sub.min indicates the smaller value of .alpha..sub.CQI and
.alpha..sub.DATA. Also, B indicates a quantization level. Also,
when an interval (e.g., 0 through 2) usable as the .alpha. value is
divided into m-ary intervals, .DELTA..sub.k indicates an SNR
difference of .alpha. values of a k-th interval and can be
calculated as C/A.sup.k. Here, C denotes a scale parameter, and A
denotes an increase range. In so doing, A.sup.k indicates that, as
the .alpha. value decreases, a performance gap between the .alpha.
values increases.
For example, referring to FIG. 6, the .alpha. value can be divided
to 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.1, and 2.0. At this time,
.DELTA..sub.3 can indicate an SNR difference 601 when .alpha. is
0.5 and when .alpha. is 0.6. FIG. 6 shows that the performance gap
increases by sqrt(2) times as the .alpha. value decreases by
0.1.
According to an embodiment, .DELTA..sub.k can be pre-calculated and
arranged in a table. According to another embodiment, by
pre-calculating and arranging the mismatch metric M in the table
based on .alpha..sub.CQI and .alpha..sub.DATA, the actual operation
may omit the calculation process of Equation 3 and retrieve the
mismatch metric based on the first alpha value and the second alpha
value from the pre-stored table. For example, assuming that the
performance gap by the difference of the a value increases by
sqrt(2) times as .alpha. decreases by 0.1, the mismatch metric
based on .alpha..sub.CQI and .alpha..sub.DATA can be calculated by
setting A= {square root over (2)}, B=10, and C=9.5, and a table
1501 showing the mismatch metric M.sub..alpha. corresponding to
.alpha..sub.CQI and .alpha..sub.DATA can be stored as shown in FIG.
15. The values of .alpha..sub.CQI, .alpha..sub.DATA, and
M.sub..alpha. in the table 1501 of FIG. 15 are exemplary values,
and it is evident that they can vary according to A, B, and C
values.
Next, the terminal 151 can determine a decoding operation using the
mismatch metric in step 125. In detail, the terminal 101 can
compare the mismatch metric calculated based on the difference
value between the first alpha value and the second alpha value with
a preset at least one threshold, and then determine the decoding
operation according to a comparison result. For example, according
to the comparison result of the mismatch metric and the threshold,
the terminal 101 may not attempt the decoding of corresponding
data, can adjust at least one decoding parameter (e.g., the number
of decoding iterations, the number of global iterations of Bit
Interleaved Coded Modulation (BICM), an nm value in sub-optional
non-binary decoding), or can determine whether to decode with the
decoding parameter assumed in the CQI calculation. The method for
determining the decoding operation according to the comparison
result shall be elucidated.
Next, the terminal 101 can decode the data received in step 119
based on the determined decoding operation in step 127, and report
information about a data decoding result and the mismatch metric to
the base station 103 in step 129. For example, the decoding result
can include ACKnowledge (ACK)/Non-ACK (NACK) indicating whether or
not the received data is successfully decoded. According to an
embodiment, when the mismatch metric value is below a certain
level, the terminal 101 can send a scheduling request message for
resource allocation to the base station 103.
Next, the base station 103 can perform scheduling for the terminal
101 based on at least one of the decoding result and the mismatch
metric received from the terminal 101 in step 131. For example, the
base station 103 can compare the mismatch metric received from the
terminal 101 with at least one threshold, and determine a Hybrid
Automatic Repeat reQuest (HARQ) related control operation for the
data based on the comparison result. For example, the base station
103 can determine which one of chase combining, retransmission, and
Incremental Redundancy (IR) is conducted on corresponding data.
Here, the HARQ related control method of the base station 103 shall
be elucidated.
For example, the base station 103 can perform the scheduling to
allocate a more reliable resource to the corresponding terminal 101
based on the mismatch metric received from the terminal 101.
According to various embodiments of the present invention, the base
station 103 can change the resource to be allocated to the terminal
101 based on the mismatch metric received from the terminal 101.
For example, each base station 103 for each cell can divide and
operate the whole resource region in a resource region 1100 fixedly
allocated for FQAM and a resource region 1110 dynamically allocable
for FQAM and QAM as shown in FIG. 11A. In so doing, the base
station 103 can determine whether to allocate the terminal 101 the
fixed resource region 1100 for the FQAM or the dynamically
allocable resource region 1110 based on the mismatch metric
received from the terminal 101.
For example, as shown in FIG. 11A, when a mismatch metric for a
terminal 0 (User 0) of a cell 0 using the fixed resource region
1100 is greater than a preset threshold and a mismatch metric for a
terminal 1 (User 1) of the cell 0 using the dynamically allocable
resource region 1110 is smaller than a preset threshold, the base
station 103 can schedule to allocate the fixed resource region 1100
to the terminal 1 and the dynamically allocable resource region
1110 to the terminal 0 as shown in FIG. 11B.
According to another embodiment of the present invention, the base
station 103 can expand the fixed resource region 1100 for the FQAM
based on the mismatch metric received from the terminal 101, and
allocate the expanded resource region to the terminal 101. For
example, the base station 103 can perform a function for expanding
the fixed resource region 1100 for the FQAM of the base station 103
based on the number of terminals having the mismatch metric value
below a certain level, or expanding a fixed resource for the FQAM
of a neighboring base station. For example, the base station 103
can perform a function for expanding the fixed resource region 1100
for the FQAM of the base station 103 based on the number of
terminals which send the scheduling request message for the
resource allocation, or expanding a fixed resource for the FQAM of
a neighboring base station. Here, the scheduling method for the
resource allocation of the base station 103 shall be
elucidated.
FIG. 2 is a block diagram of a terminal according to an embodiment
of the present invention.
Referring to FIG. 2, the terminal 200 can include a transceiving
unit 201, a control unit 203, and a storage unit 207.
The transceiving unit 201 can transceive signals with a base
station under control of the control unit 203. For example, the
transceiving unit 201 can receive a pilot signal from the base
station. For example, the transceiving unit 201 can receive MCS
information and data from the base station. For example, the
transceiving unit 201 can send a CQI and/or a first alpha value to
the base station under the control of the control unit 203. For
example, the transceiving unit 201 can send a data decoding result
and a mismatch metric of a first alpha value and a second alpha
value to the base station under the control of the control unit
203. Here, the first alpha value can indicate an alpha value
calculated for CQI calculation, and the second alpha value can
indicate an alpha value calculated for data decoding.
While the transceiving unit 201 is configured as the single module
in the embodiment of the present invention, a transmitting unit and
a receiving unit may be separately configured according to a design
method. Also, although not depicted in the drawing, the
transceiving unit 201 can be configured by including a transmitting
unit including a plurality of encoders, a plurality of modulators,
a plurality of subcarrier mappers, a plurality of modulators, and a
plurality of Radio Frequency (RF) transmitters, and by including a
receiving unit including a plurality of decoders, a plurality of
demodulators, a plurality of subcarrier demappers, a plurality of
demodulators, and a plurality of RF receivers. The transceiving
unit 201 according to an embodiment of the present invention can
include a plurality of modulators and perform the FQAM modulation.
The transceiving unit 201 according to an embodiment of the present
invention can include a plurality of demodulators, and thus decode
data under control of a decoding operation determining unit 205 or
omit the decoding. Also, the transceiving unit 201 according to an
embodiment of the present invention can perform the decoding
operation based on at least one decoding parameter adjusted by the
decoding operation determining unit 205.
The control unit 203 controls and processes general operations of
the terminal 200. The control unit 203 controls and processes to
estimate a channel between the terminal 200 and the base station,
to report information of the estimated channel to the base station,
to receive MCS information and data from the base station, to
decode data, and to send a decoding result to the base station. In
particular, according to an embodiment of the present invention,
the control unit 203 controls and processes functions for
calculating a mismatch metric based on a difference of a first
alpha value for CQI calculation and a second alpha value for data
decoding, and determining a decoding operation based on the
calculated mismatch metric. Also, in the CQI calculation, the
control unit 203 controls and processes functions for determining
at least one decoding parameter for the decoding operation, and
then decoding the data received from the base station based on at
least one decoding parameter.
For example, the control unit 203 controls and processes functions
for calculating a first alpha value for CQI calculation based on a
pilot signal reception result from the base station, and
calculating a second alpha value for data decoding based on MCS and
data reception result from the base station. Herein, the first
alpha value and the second alpha value can be, as explained in FIG.
1, calculated based on Equations 1 and 2. The decoding operation
determining unit 205 calculates the mismatch metric based on the
difference of the first alpha value and the second alpha value.
Herein, as explained in FIG. 1, the mismatch metric can be
calculated using Equation 3, or retrieved using the table 1501 of
FIG. 15.
The decoding operation determining unit 205 can calculate the
mismatch metric for the alpha values and then determine the
decoding operation by comparing the calculated mismatch metric with
at least one threshold. For example, while the decoding operation
determining unit 205 determines at least one decoding parameter for
the decoding operation in the CQI calculation, since the decoding
performance using the decoding parameter determined in the CQI
calculation may not be efficient because channel states of the CQI
calculation time and the data reception time are different, it
controls and processes an operation for controlling the decoding
parameter based on the mismatch metric for the alpha values for the
sake of the efficient decoding operation reflecting the changed
channel state.
To determine the decoding operation according to a size of the
mismatch metric for the alpha values, the decoding operation
determining unit 205 can use three thresholds, that is,
THR.sub.FAIL, THR.sub.NORMAL, and THR.sub.GOOD. Here, THR.sub.FAIL,
THR.sub.NORMA, and THR.sub.GOOD can satisfy relations of
THR.sub.FAIL<THR.sub.NORMA<THR.sub.FAIL. Alternatively,
THR.sub.FAIL can satisfy THR.sub.FAIL<0. According to an
embodiment, THR.sub.NORMA can be 0. When the mismatch metric value
is smaller than THR.sub.FAIL (M<THR.sub.FAIL<0), the decoding
operation determining unit 205 can determine that the non-Gaussian
level is greatly degraded and the data decoding success is
difficult, and control to send the NACK immediately without
attempting decoding the received data. For example, as shown in
FIG. 7, when the first alpha value .alpha..sub.CQI for the CQI
calculation is 0.3 and the second alpha value .alpha..sub.DATA for
the data decoding is 0.4, the decoding operation determining unit
205 can determine that a probability of the decoding failure is
very high because of considerable decoding performance gap due to a
difference 701 of the first alpha value .alpha..sub.CQI and the
second alpha value .alpha..sub.DATA, omit the decoding operation
for the received data, and control to send the NACK indicating the
decoding failure to the base station.
For example, as shown in FIG. 16, when the number of the decoding
iterations is continually increased, a higher performance gain can
be obtained. However, as the number of the decoding iterations
rises, system complexity increases and accordingly the number of
the decoding iterations in the system is limited. Hence, when the
mismatch metric is smaller than THR.sub.FAIL, even when additional
decoding iterations are conducted as many as the maximum number of
the decoding iterations, the embodiment of the present invention
can determine that the probability of the decoding fail is great
and omit the decoding operation for the received data. For example,
as shown in FIG. 7, when the alpha value is changed from 0.3 to
0.4, the decoding performance gap is quite considerable.
Accordingly, although the additional performance gain of 1 dB is
obtained by adding ten decoding iterations which can be executed as
much as possible, the decoding operation determining unit 205 can
determine that the probability of the decoding fail is great and
omit the decoding operation for the received data.
When the mismatch metric value is smaller than THR.sub.NORMAL and
greater than THR.sub.FAIL (THR.sub.FAIL<M<THR.sub.NORMAL),
the decoding operation determining unit 205 can determine that the
non-Gaussian level is quite degraded and it is difficult to
successfully decode corresponding data with a pre-calculated
decoding parameter, and adjust the decoding parameter though the
decoding complexity is increased. For example, as shown in FIG. 8,
when the first alpha value .alpha..sub.CQI for the CQI calculation
is 0.8 and the second alpha value .alpha..sub.DATA for the data
decoding is 0.9, the decoding operation determining unit 205 can
determine that there is a decoding performance gap due to a
difference 801 of the first alpha value .alpha..sub.CQI and the
second alpha value .alpha..sub.DATA but its performance gap is not
that great, and thus control to decode the data by adjusting the
decoding parameter value though the decoding complexity increases.
For example, the value adjustment of the decoding parameter can
include increasing the number of the decoding iterations,
increasing the number of global iterations in a BICM system,
increasing the nm value indicating a configuration set size in the
sub-optimal non-binary decoding, and so on. Here, the value of the
decoding parameter can increase in proportion to the mismatch
metric value.
Particularly, the decoding operation determining unit 205 can
determine the number of the additional decoding iterations such
that the number of the decoding iterations increases by a
particular number of times based on the mismatch metric. For
example, the number of the decoding iterations can be determined
with floor(-10*M), or using a table showing relations of the
mismatch metric and the number of the additional decoding
iterations. When the mismatch metric value is greater than
THR.sub.NORMAL and smaller than THR.sub.GOOD
(THR.sub.NORMAL<M<THR.sub.GOOD the decoding operation
determining unit 205 can determine that change of the non-Gaussian
level is slight and determine to decode with the decoding parameter
pre-calculated in the CQI calculation.
When the mismatch metric value is greater than THR.sub.GOOD
(THR.sub.GOOD<M), the decoding operation determining unit 205
can determine that the non-Gaussian level is improved, determine
that corresponding data can be fully decoded with the
pre-calculated decoding parameter, and adjust the decoding
parameter so as to lower the decoding complexity. For example, as
shown in FIG. 9, when the first alpha value .alpha..sub.CQI for the
CQI calculation is 0.4 and the second alpha value .alpha..sub.DATA
for the data decoding is 0.3 (901), the decoding operation
determining unit 205 can determine a very high probability of the
successful decoding with the preset decoding parameter in the CQI
calculation, and thus control to decode the data by adjusting the
decoding parameter value so as to decrease the decoding complexity.
For example, the value adjustment of the decoding parameter can
include decreasing the number of the decoding iterations,
decreasing the number of global iterations in the BICM system,
decreasing the nm value indicating a configuration set size in the
sub-optimal non-binary decoding, and so on.
In particular, the decoding operation determining unit 205 can
determine the number of the decoding iterations not to decode as
many as a particular number of times based on the mismatch metric.
According to another embodiment, when the mismatch metric value is
greater than THR3 (THR.sub.GOOD<M), the decoding operation
determining unit 205 may control to decode the data with the
pre-calculated decoding parameter in the CQI calculation without
adjusting the decoding parameter.
According to an embodiment, when the mismatch metric determined by
the decoding operation determining unit 205 is smaller than a
preset threshold (e.g., THR.sub.BAD) the control unit 203 can
control and process a function for sending a scheduling request
message which requests resource allocation control, to the base
station 103. According to an embodiment, the scheduling request
message requesting the resource allocation control may be
transmitted together with a message which reports the decoding
result and the mismatch metric, or separately. According to another
embodiment, the message reporting the decoding result and the
mismatch metric may be transmitted by including a parameter
requesting the resource allocation control.
The storage unit 207 stores various data and programs required for
the operations of the terminal 200. According to an embodiment of
the present invention, the storage unit 207 can store at least one
decoding parameter information determined in the CQI calculation.
Also, the storage unit 207 can store the first alpha value for the
CQI calculation and the second alpha value for the data decoding.
Also, the storage unit 207 can store information about at least one
threshold used to determine the decoding operation according to the
mismatch metric of the alpha values.
FIG. 3 is a block diagram of a base station according to an
embodiment of the present invention.
Referring to FIG. 3, the base station can include a transceiving
unit 301, a control unit 303, and a storage unit 307.
The transceiving unit 301 can transceive signals with the terminal
101 under control of the control unit 303. For example, the
transceiving unit 301 can send a pilot signal to the terminal 101.
For example, the transceiving unit 301 can transmit MCS information
and data to the terminal 101 under the control of the control unit
303. Further, the transceiving unit 301 can receive a CQI and/or a
first alpha value from the terminal 101. Also, the transceiving
unit 301 can receive a data decoding result and mismatch metric
information of alpha values from the terminal 101.
While the transceiving unit 301 is configured as the single module
in the embodiment of the present invention, a transmitting unit and
a receiving unit may be separately configured according to a design
method. Also, although not depicted in the drawing, the
transceiving unit 301 can be configured by including a transmitting
unit including a plurality of encoders, a plurality of modulators,
a plurality of subcarrier mappers, a plurality of modulators, and a
plurality of RF transmitters, and by including a receiving unit
including a plurality of decoders, a plurality of demodulators, a
plurality of subcarrier demappers, a plurality of demodulators, and
a plurality of RF receivers. The transceiving unit 301 according to
an embodiment of the present invention can include a plurality of
modulators and perform the FQAM modulation. The transceiving unit
301 according to an embodiment of the present invention can perform
an operation for at least one of chase combining, retransmission,
and IR method under the control of the control unit 303.
The control unit 303 controls and processes general operations of
the base station 300. The control unit 303 controls and processes
functions for sending a pilot signal for channel estimation of the
terminal 101, receiving a CQI and/or a first alpha value for CQI
calculation from the terminal 200, and determining an MCS based on
the received CQI and/or first alpha value. According to an
embodiment, the control unit 303 can determine the MCS based on the
curve graph showing the MCS based on the alpha value and the SINR
as shown in FIG. 14. The control unit 303 can transmit data
together with the determined MCS to the terminal. The control unit
303 can receive information about the data decoding result and the
mismatch metric value of the alpha values from the terminal, and
perform scheduling for the terminal based on the receive data
decoding result and the mismatch metric value of the alpha
values.
In particular, when the data decoding result received from the
terminal 101 is NACK, a terminal scheduling control unit 305 can
control an HARQ operation based on the mismatch metric value. For
example, to control the HARQ operation based on the mismatch metric
value, the terminal scheduling control unit 305 can use at least
two thresholds, for example, THR.sub.RET and THR.sub.CC. Here,
THR.sub.RET and THR.sub.CC can satisfy a relation of
THR.sub.RET<THR.sub.CC.
For example, when the received mismatch metric value is smaller
than THR.sub.RET, the terminal scheduling control unit 305 can
determine to conduct a retransmission method. For example, when the
received mismatch metric value is greater than THR.sub.RET and
smaller than THR.sub.CC, the terminal scheduling control unit 305
can determine to conduct a chasing combining method. For example,
when the received mismatch metric value is greater than THR.sub.CC,
the terminal scheduling control unit 305 can determine to conduct
an IR method. Herein, the retransmission method indicates a method
for attempting decoding merely with a retransmit packet when a
previous packet has an error, and the chase combining method
indicates a method for attempting decoding by combining the
original packet having error with the retransmit packet. Also, the
IR method indicates a method for performing the retransmission by
gradually increasing a channel coding gain in every retransmission
time.
For example, as shown in FIG. 10, when the first alpha value
.alpha..sub.CQI calculated in the terminal 101 for the CQI
calculation is 0.3 and the second alpha value .alpha..sub.DATA for
the data decoding is 0.4 (1001), the terminal scheduling control
unit 305 can determine to perform the retransmission method because
the IR method is impossible due to great decoding performance gap
based on a difference of the first alpha value .alpha..sub.CQI and
the second alpha value .alpha..sub.DATA. By contrast, as shown in
FIG. 10, when the first alpha value .alpha..sub.CQI calculated in
the terminal 101 for the CQI calculation is 0.8 and the second
alpha value .alpha..sub.DATA for the data decoding is 0.9 (1003),
the terminal scheduling control unit 305 can determine that the IR
method is feasible because of small decoding performance gap based
on the difference of the first alpha value .alpha..sub.CQI and the
second alpha value .alpha..sub.DATA and determine to perform the IR
method.
Additionally, when the received mismatch metric value is smaller
than THR.sub.BAD, the terminal scheduling control unit 305 can
allocate a fixed resource region for the FQAM to the corresponding
terminal. THR.sub.BAD can satisfy a relation of
THR.sub.BAD<THR.sub.RET or a relation of
THR.sub.BAD<THR.sub.CC. As shown in FIG. 11A, the terminal
scheduling control unit 305 can separately operate the resource
region 1100 fixedly allocated for the FQAM and the resource region
1110 dynamically allocable for the FQAM and the QAM. For example,
the terminal scheduling control unit 305 can allocate the fixed
resource region 1100 only to terminals supporting the FQAM, and
allocate the dynamically allocable resource region 1110 to
terminals supporting the FQAM and terminals supporting the QAM.
According to an embodiment of the present invention, the terminal
scheduling control unit 305 can change the resources allocated to
the terminals based on the mismatch metric value received from a
plurality of terminals serviced by the base station. For example,
as shown in FIG. 11A, when a terminal 0 of terminals 0, 1, and 2
supporting the FQAM is allocated to the fixed resource region 1100,
the terminals 1 and 2 are allocated to the dynamically allocable
resource region 1110, a mismatch metric value of the terminals 0
and 2 of the cell 0 is greater than THR.sub.BAD, and a mismatch
metric value of the terminal 1 is smaller than THR.sub.BAD, the
terminal scheduling control unit 305 can allocate the fixed
resource region 1110 to the terminal 1 and the dynamically
allocable resource region 1110 to the terminal 0 as shown in FIG.
11B.
For example, terminals located on a cell boundary among the
terminals serviced from the base station can increase the change of
the alpha value due to interference of a downlink channel of a
neighboring cell, and thus the mismatch metric value can be smaller
than THR.sub.BAD. In this case, the base station can reduce the
change of the alpha value of a corresponding terminal by changing
the resource allocation region for the corresponding terminal.
Hence, the embodiment of the present invention can induce not to
change the alpha value by changing and allocating the resource
region to the terminal of which the mismatch metric value is
smaller than THR.sub.BAD.
According to another embodiment, the terminal scheduling control
unit 305 can exchange information about the mismatch metric value
received from the multiple terminals serviced from the base
station, with a neighboring base station, and perform resource
allocation scheduling based on the exchanged information. For
example, as shown in FIG. 12, when a base station of each cell
allocates different resource regions to terminals connected to each
base station and the alpha value of the terminal 1 (user 1)
connected to the base station of the cell 0 is changed, the base
station (e.g., the terminal scheduling control unit 305) of the
cell 0 can receive the mismatch metric value indicating the change
of the alpha value from the terminal 1 and send the received
mismatch metric value to base stations of the cell 1, the cell 2,
and the cell 3. Hence, based on the mismatch metric value of the
terminal 1 belonging to the base station of the cell 0, the base
stations of the cells 1, 2, and 3 can change a purpose of resource
regions 1301 through 1304, 1311 through 1315 of the cell 1, the
cell 2, and the cell 2 corresponding to resource regions 1300 and
1310 allocated to the terminal 1 of the cell 0 as shown in FIG.
13B.
For example, when the alpha value of the terminal 1 connected to
the cell 0 increases from 0.9 to 2.0, the cell 1, the cell 2, and
the cell 3 (or a base station 1 of the cell 1, a base station 2 of
the cell 2, and a base station 3 of the cell 3) can allocate the
resource regions 1301 through 1304 corresponding to the resource
region 1300 used by the terminal 1 of the cell 0, to the terminal
supporting the QAM, not the FQAM, based on the mismatch metric
value indicating the alpha value increase of the terminal 1
connected to the cell 0 from the cell 0, as shown in FIG. 13A. That
is, the cell 1, the cell 2, and the cell 3 confirm the increase of
the alpha value based on the mismatch metric of the terminal 1 of
the cell 0, do not allocate the resource regions 1301 through 1304
corresponding to the resource region 1300 used by the terminal 1 of
the cell 0, to the terminal supporting the FQAM, and thus can
minimize downlink interference for the terminal 1 of the cell
0.
For example, when the alpha value of the terminal 1 connected to
the cell 0 decreases from 0.9 to 0.6, the cell 1, the cell 2, and
the cell 3 can allocate the resource regions 1311 through 1315
corresponding to the resource region 1310 used by the terminal 1 of
the cell 0, to the terminal supporting the FQAM or the terminal
supporting the QAM, based on the mismatch metric value indicating
the alpha value decrease of the terminal 1 connected to the cell 1.
That is, the cell 1, the cell 2, and the cell 3 can confirm the
decrease of the alpha value based on the mismatch metric of the
terminal 1 of the cell 0, and allocate the terminal supporting the
FQAM or the QAM to the resource regions 1301 through 1304
corresponding to the resource region 1300 used by the terminal 1 of
the cell 0.
Additionally, the terminal scheduling control unit 305 can expand
the fixed resource region for the FQAM in the whole resource region
based on the mismatch metric received from the terminal 101, and
allocate the expanded resource region to the terminal supporting
the FQAM. According to an embodiment of the present invention, the
terminal scheduling control unit 305 can perform a function for
expanding the fixed resource region for the FQAM of the base
station based on the number of terminals of which the mismatch
metric value is below a certain level (e.g., THR.sub.BAD or a
separate THR), or expanding the fixed resource for the FQAM of the
neighboring base station. For example, when the number of the
terminals having the mismatch metric value below the certain level
is greater than a predefined number of thresholds, the terminal
scheduling control unit 305 can request a higher node to expand the
size of the fixed resource region for the FQAM. For example, the
terminal scheduling control unit 305 can report the number of
terminals reporting the mismatch metric below the certain level, to
the higher node. In this case, the higher node can determine
whether to expand the fixed resource region for the FQAM based on
the number of the terminals reported from the base station, and
expand the fixed resource region for the FQAM. For example, when
the number of the terminals having the mismatch metric value below
the certain level is greater than a predefined number of
thresholds, the terminal scheduling control unit 305 can request
the fixed resource region expansion for the FQAM from a neighboring
cell connected with an X2 interface.
According to another embodiment of the present invention, the
terminal scheduling control unit 305 can perform a function for
expanding the fixed resource region for the FQAM based on the
number of terminals sending the scheduling request message for the
resource allocation, or expanding the fixed resource for the FQAM
of the neighboring base station. For example, when the number of
the terminals sending the scheduling request message is greater
than a predefined number of thresholds, the terminal scheduling
control unit 305 can request the high mode of the base station to
expand the size of the fixed resource region for the FQAM. For
example, the terminal scheduling control unit 305 can report the
number of the terminals sending the scheduling request message for
the resource allocation, to the higher node. In this case, the
higher node can determine whether to expand the fixed resource
region for the FQAM based on the number of the terminals reported
from the base station, and expand the fixed resource region for the
FQAM. For example, when the number of the terminals sending the
scheduling request message for the resource allocation is greater
than a predefined number of thresholds, the terminal scheduling
control unit 305 can request the fixed resource region expansion
for the FQAM from a neighboring cell connected with an X2
interface.
The storage unit 307 stores various data and programs for the
operations of the base station 300. Also, the storage unit 307 can
store data to send to the terminal 101, and MCS information for the
terminal, and can store information about the mismatch metric value
received from the terminal 101. Also, the storage unit 307 can
store HARQ information and scheduling information relating to each
terminal.
FIG. 4 is a flowchart illustrating a procedure for decoding data
based on a mismatch metric of alpha values in a terminal according
to an embodiment of the present invention.
Referring to FIG. 4, the terminal 101 can receive a pilot signal
from a base station in step 401, and calculate a first alpha value
for CQI calculation in step 403. For example, using Equations 1 and
2, the terminal 101 can calculate the first alpha value for the CQI
calculation based on a pilot signal reception result from the base
station.
After calculating the first alpha value, the terminal 101 can
calculate the CQI based on the calculated first alpha value in step
405. For example, as shown in FIG. 14, the terminal 101 can
determine, as the CQI, a modulation scheme and a coding rate
corresponding to an SNR of the pilot signal and the calculated
first alpha value using a pre-obtained curve graph. For example,
when the SNR is 8.8 dB and the first alpha value is 0.5, the
terminal 101 can determine a modulation level as 16FQAM including
4FSK and 4QAM and determine a coding rate as 1/3. Here, the curve
graph showing the CQI based on the SNR and the alpha value can be
obtained or stored in advance through experiments.
Next, the terminal 101 can receive data from the base station in
step 407, and calculate a second alpha value for data decoding in
step 409. For example, using Equation 1 and Equation 2, the
terminal 101 can calculate the second alpha value for the data
decoding based on the MSC and the data reception result from the
base station.
Next, the terminal 101 determines a mismatch metric according to a
difference of the first alpha value and the second alpha value. For
example, the terminal 101 can determine the mismatch metric based
on Equation 3. For example, as shown in FIG. 15, the terminal 101
can obtain the mismatch metric according to the difference of the
first alpha value and the second alpha value from the table 1501
showing the mismatch metric M.sub..alpha. corresponding to
.alpha..sub.CQI and .alpha..sub.DATA. Herein, the values of
.alpha..sub.CQI, .alpha..sub.DATA, and M.sub..alpha. in the table
1501 of FIG. 15 are exemplary values, and it is evident that they
can vary according to A, B, and C values as described in Equation
3. Next, the terminal 101 can determine a decoding operation based
on the determined mismatch metric in step 413. For example, the
terminal 101 can calculate the mismatch metric for an alpha value
change range, and then determine the decoding operation by
comparing the calculated mismatch metric with at least one
threshold. Next, the terminal 101 can decode the data through the
determined decoding operation in step 415.
For example, when the mismatch metric value is smaller than
THR.sub.FAIL, the terminal 101 can determine that it is hard to
succeed in the data decoding, and may not attempt to decode the
received data. In this case, the terminal 101 can send a NACK to
the base station. For example, as shown in FIG. 7, when the first
alpha value .alpha..sub.CQI for the CQI calculation is 0.3 and the
second alpha value .alpha..sub.DATA for the data decoding is 0.4,
the terminal 101 can determine that the probability of the decoding
failure is very high because of considerable decoding performance
gap due to the difference 701 of the first alpha value
.alpha..sub.CQI and the second alpha value .alpha..sub.DATA, omit
the decoding operation for the received data, and send the NACK
indicating the decoding failure to the base station.
For example, when the mismatch metric value is smaller than
THR.sub.NORMAL and greater than THR.sub.FAIL, the terminal 101 can
fulfill the decoding by adjusting the decoding parameter so as to
increase the decoding complexity. For example, as shown in FIG. 8,
when the first alpha value .alpha..sub.CQI for the CQI calculation
is 0.8 and the second alpha value .alpha..sub.DATA for the data
decoding is 0.9, the terminal 101 can determine that there is the
decoding performance gap due to the difference 801 of the first
alpha value .alpha..sub.CQI and the second alpha value
.alpha..sub.DATA but its performance gap is not that great, and
thus control to decode the data by adjusting the decoding parameter
value though the decoding complexity increases.
For example, the decoding parameter value adjustment can include
increasing the number of the decoding iterations, increasing the
number of global iterations in a BICM system, increasing the nm
value indicating a configuration set size in the sub-optimal
non-binary decoding, and so on. Here, the value of the decoding
parameter can increase in proportion to the mismatch metric value.
In particular, the terminal 101 can determine the number of the
additional decoding iterations based on the mismatch metric such
that the number of the decoding iterations increases by a specific
number of times.
For example, when the mismatch metric value is greater than
THR.sub.NORMAL and smaller than THR.sub.GOOD, the terminal 101 can
determine that the change of the non-Gaussian level is slight and
decode with the decoding parameter pre-calculated in the CQI
calculation.
For example, when the mismatch metric value is greater than
THR.sub.GOOD, the terminal 101 can determine that the non-Gaussian
level is improved, determine that corresponding data can be fully
decoded with the pre-calculated decoding parameter, and adjust the
decoding parameter so as to decrease the decoding complexity. For
example, as shown in FIG. 9, when the first alpha value
.alpha..sub.CQI for the CQI calculation is 0.4 and the second alpha
value .alpha..sub.DATA for the data decoding is 0.3 (901), the
terminal 101 can determine the very high probability of the
successful decoding with the preset decoding parameter in the CQI
calculation, and decode the data by adjusting the decoding
parameter value so as to decrease the decoding complexity.
For example, the decoding parameter value adjustment can include
increasing the number of the decoding iterations, increasing the
number of the global iterations in the BICM system, increasing the
nm value indicating the configuration set size in the sub-optimal
non-binary decoding, and so on. In particular, the terminal 101 can
determine the number of the decoding decrease based on the mismatch
metric not to perform the decoding a specific number of times.
Next, the terminal 101 can finish the procedure according to an
embodiment of the present invention.
FIG. 5 illustrates a procedure for scheduling data based on a
mismatch metric of alpha values in a base station according to an
embodiment of the present invention.
Referring to FIG. 5, the base station 103 can receive a decoding
result and a mismatch metric from the terminal 101 in step 501, and
perform scheduling for the terminal 101 based on the received
decoding result and mismatch metric in step 503. According to
various embodiments of the present invention, when the data
decoding result received from the terminal 101 is a NACK, the base
station 103 can control an HARQ operation based on the mismatch
metric value.
For example, the base station 103 can compare the received mismatch
metric value with at least one threshold, and thus determine to
conduct any one of a chase combining method, a retransmission, and
an IR. For example, when the mismatch metric value received from
the terminal 101 is smaller than THR.sub.REI, the base station 103
can determine to conduct the retransmission method. For example,
when the mismatch metric value received from the terminal 101 is
greater than THR.sub.RET and smaller than THR.sub.CC, the base
station 103 can determine to conduct the chasing combining method.
For example, when the mismatch metric value received from the
terminal 101 is greater than THR.sub.CC, the base station 103 can
determine to conduct the IR method.
According to various embodiments of the present invention, the base
station 103 can allocate a different resource to the terminal 101
based on the received mismatch metric value. For example, when a
mismatch metric value received from a particular terminal 101 is
smaller than THR.sub.BAD, the base station 103 can allocate a fixed
resource region for FQAM of the whole resource region of the base
station, to the particular terminal 101. For example, the base
station 103 can perform functions for expanding the fixed resource
region for the FQAM based on the number of terminals reporting the
mismatch metric value smaller than THR.sub.BAD, and allocating the
expanded FQAM fixed resource region to terminals which report the
mismatch metric value smaller than THR.sub.BAD.
For example, the base station 103 can perform a function for
expanding the fixed resource region for the FQAM of a neighboring
base station based on the number of terminals reporting the
mismatch metric value smaller than THR.sub.BAD. For example, the
base station 103 can perform functions for expanding the fixed
resource region for the FQAM based on the number of terminals which
send a scheduling request message for resource allocation, and
allocating the expanded FQAM fixed resource region to the terminals
which send the scheduling request message. For example, the base
station 103 can perform a function for expanding the fixed resource
region for the FQAM of the neighboring base station based on the
number of terminals which send the scheduling request message. For
example, the base station 103 can perform functions for exchanging
with the neighboring base station, information about a mismatch
metric reported from a terminal connected to each base station, and
allocating a resource region based on the exchanged
information.
Next, the base station 103 can finish the procedure according to an
embodiment of the present invention.
FIG. 6 is a graph showing a decoding performance difference
determined by an alpha value in a terminal according to an
embodiment of the present invention.
Referring to FIG. 6, the .alpha. value can be divided to 0.3, 0.4,
0.5, 0.6, 0.7, 0.8, 0.9, 1.1, and 2.0. At this time, .DELTA..sub.3
can denote the SNR difference 601 when .alpha. is 0.5 and when
.alpha. is 0.6.
FIG. 7 is a graph for determining a decoding method of a terminal
according to an alpha value in a terminal according to an
embodiment of the present invention.
Referring to FIG. 7, when the first alpha value .alpha..sub.CQI for
the CQI calculation is 0.3 and the second alpha value
.alpha..sub.DATA for the data decoding is 0.4, the terminal 101 can
determine that the probability of the decoding failure is very high
because of the considerable decoding performance gap due to the
difference 701 of the first alpha value .alpha..sub.CQI and the
second alpha value .alpha..sub.DATA. The terminal 101 can abort the
decoding operation for the data received from the base station 103,
and send the NACK indicating the decoding failure to the base
station 103.
FIG. 8 is a graph for determining a decoding method of a terminal
according to an alpha value in the terminal according to another
embodiment of the present invention.
Referring to FIG. 8, when the first alpha value .alpha..sub.CQI for
the CQI calculation is 0.8 and the second alpha value
.alpha..sub.DATA for the data decoding is 0.9, the terminal 101 can
determine that there is the decoding performance gap due to the
difference 801 of the first alpha value .alpha..sub.CQI and the
second alpha value .alpha..sub.DATA but its performance gap is not
that great. The terminal 101 can decode data by adjusting the
decoding parameter value though the decoding complexity
increases.
FIG. 9 is a graph for determining a decoding method of a terminal
according to an alpha value in the terminal according to yet
another embodiment of the present invention.
Referring to FIG. 9, when the first alpha value .alpha..sub.CQI for
the CQI calculation is 0.4 and the second alpha value
.alpha..sub.DATA for the data decoding is 0.4 (901), the terminal
101 can determine the very high probability of the decoding success
with a current decoding parameter in the CQI calculation. The
terminal 101 can decode data by reducing the decoding parameter
value so as to decrease the decoding success probability and to
lower the decoding complexity.
FIG. 10 is a graph for performing HARQ based on a decoding result
in a base station according to an embodiment of the present
invention.
Referring to FIG. 10, when the first alpha value .alpha..sub.CQI
calculated in the terminal 101 for the CQI calculation is 0.3 and
the second alpha value .alpha..sub.DATA for the data decoding is
0.4 (1001), the base station 103 can determine that the IR method
is impossible due to the great decoding performance gap based on
the difference of the first alpha value .alpha..sub.CQI and the
second alpha value .alpha..sub.DATA. Hence, the base station 103
can transmit data by conducting the retransmission method.
By contrast, when the first alpha value .alpha..sub.CQI calculated
in the terminal 101 for the CQI calculation is 0.8 and the second
alpha value .alpha..sub.DATA for the data decoding is 0.9 (1003),
the base station 103 can determine that the IR method is feasible
because of the small decoding performance gap based on the
difference of the first alpha value .alpha..sub.CQI and the second
alpha value .alpha..sub.DATA. Thus, the base station 103 can
transmit data by conducting the IR method.
Although the detailed description of the present invention has
described a specific embodiment, the system, the apparatus, and the
method described in the present specification may be corrected,
added, or omitted as far as they do not depart from the scope of
the present invention. For example, elements and devices of the
system may combine or separated. Further, operations of the system
and the device may be executed by more devices or less devices, or
other devices. The method can include more steps, less steps, or
other steps. Also, steps can combine and/or be executed in an
arbitrary proper sequence.
As above, while the present invention has been described with the
limited embodiments and drawings, the present invention is not
limited to those embodiments and those skilled in the art to which
the present invention belongs can make various modifications and
changes based on this disclosure. Operations according to the
embodiments of the present invention can be implemented by a single
processor. In this situation, program instructions for performing
an operation implemented by various computers can be recorded on a
computer-readable medium. The computer-readable medium can include
a program instruction, a data file, a data structure, and the like,
alone or in combination. The program instruction can be specially
designed and configured for the present invention or known to and
usable by one skilled in the art. Example of a computer-readable
recording medium include a hard disk, a magnetic medium such as a
floppy disk and a magnetic tape, an optical recording medium such
as a Compact Disc (CD)-Read Only Memory (ROM) and a Digital Video
Disc (DVD), a magneto-optical medium such as a floptical disk, and
a hardware device specially configured for storing and performing a
program instruction such as ROM, Random Access Memory (RAM), a
flash memory, and the like An example of the program instruction
includes not only a machine language code generated by a compiler
but also a high-level language code executable by a computer using
an interpreter. When whole or part of a base station or a relay
described in the present invention is realized as a computer
program, the present invention also includes a computer-readable
recording medium storing the computer program.
The present invention is described with exemplary embodiments, but
various variations and modifications can be suggested to those
skilled in the art. The present invention is intended to cover
modifications and variations which fall within the appended
claims.
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